Non-small-cell lung cancer (NSCLC) accounts for approximately 80% of all lung cancers, with 1.2 million new cases worldwide each year. NSCLC resulted in more than one million deaths worldwide in 2001 and is the leading cause of cancer-related mortality in both men and women (31% and 25%, respectively). The prognosis of advanced NSCLC is dismal. A recent Eastern Cooperative Oncology Group trial of 1155 patients showed no differences among the chemotherapies used: cisplatin/paclitaxel, cisplatin/gemcitabine, cisplatin/docetaxel and carboplatin/paclitaxel. Overall median time to progression was 3.6 months, and median survival was 7.9 months.
The overall five-year survival of patients with NSCLC has remained at less than 15% for the past 20 years. Stage grouping of TNM subsets (T=primary tumor; N=regional lymph nodes; M=distant metastases) permits the identification of patient groups with similar prognosis and treatment options. Five-year survival is around 25% for pathologic stage IIB (T1-2N1M0, T3N0M0), 13% for stage IIIA (T3N1M0, T1-2-3N2M0), and a low 7% for stage IIIB (T4N0-1-2M0).
Currently, cisplatin (DDP) and carboplatin are among the most widely used cytotoxic anticancer drugs. However, resistance to these drugs through de novo or induced mechanisms undermines their curative potential. These drugs disrupt DNA structure through formation of intrastrand adducts. Resistance to platinum agents such as DDP has been attributed to enhanced tolerance to platinum adducts, decreased drug accumulation, or enhanced DNA repair.
Small randomized studies of cisplatin-based chemotherapy followed by surgery in clinical stage IIIA (Pass HI, et al. (1992) Ann. Thor. Surg., 53, 992-998: “Randomized trial of neoadjuvant therapy for lung cancer: interim analysis”) or stage IIB-IIIB (Rosell R, et al. (1994) N. Engl. J. Med., 330, 153-158 “A randomized trial comparing preoperative chemotherapy plus surgery with surgery alone in patients with non-small-cell lung cancer”) showed remarkable improvement in survival over NSCLC patients treated either with surgery alone or with surgery followed by radiotherapy. Event-free survival was similar in the two studies (12.7 and 20 months in the neoadjuvant chemotherapy arm and 5.8 and 5 months in the surgery arm). In general, neoadjuvant chemotherapy induces tumor shrinkage and sterilizes metastatic lymph nodes, leading to pathologic downstaging in approximately 33% and complete pathologic remission in up to 14% of patients.
During the past 30 years medical oncologists have focused to optimise the outcome of cancer patients and it is just now that the new technologies available are allowing to investigate polymorphisms, gene expression levels and gene mutations aimed to predict the impact of a given therapy in different groups of cancer patients to tailor chemotherapy. Representative examples include the relation between the TS mRNA expression and the response and the survival with antifolates (see EP 1 381 691), beta tubulin III mRNA levels and response to tubulin interacting agents, PTEN methylation and resistance to CPT-11 and STAT3 over expression and resistance to EGF interacting agents.
Although a wealth of data indicates that changes in the level of several gene transcripts can modulate differential chemosensitivity between NSCLC patients with the same TNM subset, at present no predictive genetic markers of chemotherapy response are used for tailoring treatment. To further improve the survival rate in patients with Non-Small Cell Lung Carcinoma (NSCLC), their prognostic classification based on molecular alterations is crucial. Such classification will provide more accurate and useful diagnostic tools and, eventually, more effective therapeutic options.
Breast Cancer 1 (BRCA1) plays a crucial role in DNA repair, and decreased BRCA1 mRNA expression has been observed in both sporadic and hereditary breast cancers (Kennedy R D, et al. (2002) Lancet, 360, 1007-1014: “BRCA1: mechanisms of inactivation and implications for management of patients”). However, its potential effect in lung cancer has never been examined.
BRCA1 is implicated in transcription-coupled nucleotide excision repair (TC-NER), and modulation of its expression leads to modification of TC-NER and hence to radio- and chemoresistance. Upregulation of BRCA1 expression led to increased cisplatin resistance in the SKOV-3 human ovarian cancer cell line (Husain A, et al. (1998) Cancer Res., 58, 1120-1123: “BRCA1 up-regulation is associated with repair-mediated resistance to cis-diamminedichloroplatinum(II)”), and restoration of BRCA1 in the BRCA1-negative HCC1937 human breast cancer cell line restored radioresistance. BRCA1 is also involved in homologous recombination repair (HRR) and non-homologous end joining in response to DNA damage. In addition, it is a component of a large DNA repair complex termed the BRCA1-associated genome surveillance complex, which contains a number of mismatch repair proteins, indicating a potential role for BRCA1 in mismatch repair. BRCA1 may also be a regulator of mitotic spindle assembly, as BRCA1 and β-tubulin colocalize to the microtubules of the mitotic spindle and to the centrosomes. Finally, enhanced BRCA1 expression has been linked to apoptosis through the c-Jun N-terminal kinase pathway, which is activated by cisplatin-induced DNA damage; inhibition of this pathway increased cisplatin sensitivity in cell lines. Decreased BRCA1 mRNA expression in a breast cancer cell line, as determined by real-time quantitative polymerase chain reaction (RT-QPCR), led to greater sensitivity to cisplatin and etoposide but to greater resistance to the microtubule-interfering agents paclitaxel and vincristine (Lafarge S, et al. (2001) Oncogene, 20, 6597-6606: “Inhibition of BRCA1 leads to increased chemoresistance to microtubule-interfering agents, an effect that involves the JNK pathway”). Recently, reconstitution of wild-type BRCA1 into the BRCA1-negative HCC1937 breast cancer cell line resulted in a 20-fold increase in cisplatin resistance and, in contrast, in a 1000-10,000-fold increase in sensitivity to antimicrotubule drugs (paclitaxel and vinorelbine).
Mouse models carrying conditional disruption of BRCA1 were highly sensitive to doxorubicin and gamma irradiation but resistant to tamoxifen, providing additional evidence for differential chemosensitivity linked to BRCA1 expression. When BRCA1 expression was examined by semi-quantitative PCR in women with sporadic breast cancer, lower BRCA1 mRNA levels (bottom quartile) were associated with a higher frequency of distant metastases (Seery L T, et al. (1999) Int. J. Cancer (Pred. Oncol.), 84, 258-262: “BRCA1 expression levels predict distant metastasis of sporadic breast cancers”. 
Despite the wealth of data in cell lines and mouse models, only one small study has examined the correlation of BRCA1 and BRCA2 mRNA expression with response to chemotherapy in the clinical setting (Egawa C., (2001) Int. J. Cancer (Pred. Oncol.), 95, 255-259: “Decreased expression of BRCA2 mRNA predicts favorable response to docetaxel in breast cancer”). Among 25 women with docetaxel-treated locally advanced or metastatic breast cancer, only BRCA2 mRNA levels were significantly lower in responders than in non-responders, though a slight difference was also observed for BRCA1.